nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89674
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:54 UTC
Updated2026-09-11 20:19:54 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget The XDR buffer size calculation in nfsd4_ff_encode_layoutget() has multiple errors that can result in either an out-of-bounds write or leaking uninitialized kernel memory to the client: - fh_len doesn't account for XDR padding on the file handle data - uid and gid lengths use "8 + len" but xdr_encode_opaque() actually writes "4 + xdr_align_size(len)" bytes - ds_len omits the flags and stats_collect_hint fields (8 bytes), while len's header constant overestimates by 8 bytes -- these partially cancel but leave a net mismatch The worst case occurs with short strings (e.g. uid=0, gid=0 with an odd-sized file handle), where the function writes up to 5 bytes past the reserved XDR buffer. Conversely, when string lengths happen to be 4-byte aligned, the reservation is too large and stale buffer content is sent to the client. Fix this by breaking out every encoded field explicitly in the ds_len calculation, using xdr_align_size() for all variable-length opaque fields, and correcting the header constants.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9b9960a0ca4773e21c4b153ed355583946346b25 e7d9d23ecd9172f05b09bb678ff22db8e361c428 git Not specified
CNA Linux Linux affected 9b9960a0ca4773e21c4b153ed355583946346b25 0380129b1373c437eb35401a174671c8888f4b80 git Not specified
CNA Linux Linux affected 9b9960a0ca4773e21c4b153ed355583946346b25 c81cef6a805dec266c10fc4f83c93d6fcf1a2b43 git Not specified
CNA Linux Linux affected 9b9960a0ca4773e21c4b153ed355583946346b25 f9868174af49d207fbaf0c5e055d088a983684af git Not specified
CNA Linux Linux affected 4.8 Not specified
CNA Linux Linux unaffected 4.8 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f9868174af49d207fbaf0c5e055d088a983684af 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c81cef6a805dec266c10fc4f83c93d6fcf1a2b43 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0380129b1373c437eb35401a174671c8888f4b80 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e7d9d23ecd9172f05b09bb678ff22db8e361c428 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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